In underground mining operations using drum-type continuous miners, water spray nozzles may be located on the cutting drum near each cutter bit to suppress the generation of airborne dust and frictional ignition as the cutter bits engage the mine face. Airborne dust and wet dislodged material may also be suppressed by mounting spray nozzles on a bar located behind the cutter drum. The bar mounted spray nozzles wet the mine material above and below the cutter drum and also wet the bits as the cutter drum completes each rotation.
The effectiveness of a spray bar is limited and may not control dust before it becomes airborne. However, the incorporation of spray nozzles located immediately adjacent the cutter bits on the surface of the cutter drum has been found to be effective in suppressing dust before it becomes airborne. The water is continuously sprayed from the cutter bits directly at the point where the material is dislodged from the mine face. Generating a water spray at the cutter bits suppresses the dust at its source and effectively eliminates any risk of frictional ignition as the cutter bits strike the solid material. Generating a water spray from the nozzles also serves to extend the life of cutter bits for continuous miners. Water is supplied to the nozzles on the surface of a continuous miner drum from a water supply on a non-rotating portion of the mining machine. For example, water is supplied from the cooling circuits of the drive motors and conveyed through conduits in stationary struts and housings to a rotary seal mounted concentrically on the axis of the drum. Conventional rotary seals are positive pressure seals designed to prevent any leakage of the water past the seals. A rotary seal has a stationary part with ports for receiving the water and a rotational part mounted on or connected to the drive shaft. In order to maintain a positive pressure seal between the stationary and rotating parts, the rotary seal typically employs an elastomeric material such as rubber, or surfaces of other materials such as carbon that are machined to extremely tight tolerances. Surfaces of the positive pressure rotary seal are in constant contact in order to form the seal. Relative rubbing motion between the parts may cause wear and eventual failure of the seal. A typical positive pressure rotary seal in a mining machine must also keep the water from leaking into contact with the gears and bearings as the water passes through the rotary seal on its way to fittings on spray nozzles associated with the cutter bits.
A critical aspect in supplying water through a cutter drum to the external surface behind the cutter bits is the effectiveness of the rotary seal in preventing leakage of water into the gearcase and bearings. With a positive pressure seal for a continuous mining machine, this problem is aggravated because a relatively large rotating seal must be used around the drive shaft of the continuous miner. The larger diameter rotary seal has more contact surface area where breakdown of the seal or other failures can occur. This problem is further complicated with continuous miners having multiple sections. A typical continuous miner includes a pair of end drum sections and a center drum section. Each section has a separate drive shaft requiring separate large diameter rotary seals. In addition to preventing contamination of the gearcase and bearings, the rotary seal must withstand periods of time in which it runs dry where water is not circulated to the seal.
A continuous mining machine is disclosed in U.S. Pat. No. 5,507,565 that issued to LeBegue et al. on Apr. 16, 1996 (“the '565 patent”). The continuous mining machine in the '565 patent provides a cutter drum assembly rotatably mounted on a boom member. Cutter bits are secured to the cutter drum assembly and extend therefrom. A gearcase is positioned in the cutter drum. A plurality of sprayers are associated with the cutting elements for spraying water onto the material being mined. Positive pressure liquid seals are positioned in the gearcase for directing liquid through the gearcase to the spray devices and preventing liquid from coming into contact with the bearing means. A lubricant seal is required surrounding the positive pressure liquid seals in the gearcase to keep the liquid seals lubricated and to act as a redundant seal to prevent liquid leakage from the liquid seals contaminating the bearings.
Although the apparatus of the '565 patent may have improved the ability to spray liquid onto the mine face as material is dislodged, while avoiding contamination of the gearcase with the liquid, the apparatus may still be problematic. In particular, the apparatus disclosed in the '565 patent requires positive pressure water seals that are subject to constant wear, and that must be relied upon to keep water from getting into the bearings and gear assemblies. Failure of one of these seals can allow water to get into the bearings or gearcase, causing catastrophic failure. The seals are also buried deep inside the assembly, making replacement or maintenance of the seals difficult. Additionally, the seals require lubrication with oil-based lubricants, and additional lubricant seals must be provided to contain the lubricants in contact with the liquid seals.
The continuous mining machine of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.